In cold regions, the brittle fracture characteristics of geomembranes should be fully considered. Generally speaking, the geotechnical composition data can tolerate the low temperature as high as (-45±2)℃, and the average coldest temperature in the north is about -32℃. The geomembrane can meet the requirements of low temperature resistance and anti-brittle crack without interference. According to laboratory tests, geomembrane plasticity disappears and brittleness increases below -5℃. Data show that it is easy to crack after disturbance. The following are the precautions and brief construction methods for geomembrane construction in winter.
1. Due to the large settlement of the dam， settlement deformation of the front dam slope in the winter operation period of the reservoir bottom should be avoided, resulting in brittle fracture of the geomembrane. Therefore, the dam should be rolled in layers according to the design standards, and water should be soaked after each layer of rolling to ensure that the dam filling is compact.
2. Impermeable geomembrane winter use performance is brittle, in order to prevent winter due to geomembrane disturbance, geomembrane brittle break, resulting in water leakage, should avoid winter laying geomembrane and may cause geomembrane disturbance, brittle break dam surface construction.
3.Impermeable geomemebrane needs to be splicing or connected with the surrounding concrete toe plate, its quality directly affects the impermeable performance of the geomembrane. Before laying the geomembrane, the construction of the underlying layer of unsanded concrete should be carried out first, and then the rolled bale geomembrane should be laid vertically along the dam slope from bottom to top. The laying should be smooth and the tightness should be moderate, and about 1.5% of the remaining width should be reserved to avoid tensile damage.
4. Frost heaving damage to lining is an important problem in the construction of cold areas, which directly affects the anti-seepage effect and the normal operation of the project. to prevent freezing damage of lining, comprehensive measures should be taken from the aspects of planning and layout, seepage control and drainage, heat insulation and heat preservation, the structural form of section, lining material, management and maintenance. the results show that the basic factors of frost heave failure are soil properties, soil moisture content (moisture content and groundwater level) and negative temperature, which are indispensable. as long as one of these factors is eliminated, frost heave will not occur.
5. For the impermeable structure of geomembrane in contact with water for a long time in cold areas, thermal insulation lining can also be used, that is thermal insulation sandwich is set between geomembrane and protective surface. suitable materials for insulation sandwich include polystyrene rigid foam board, pumice stone, ceramicized perlite and silica shale, etc. polystyrene foam board has been used as thermal insulation and antifreeze slope protection of reservoir dam and thermal insulation lining of large channel.